Fiberoptics is the branch of physics concerned with the propagation of light that enters a thread or rod of transparent material at one end and is totally reflected back inward from the wall, thereby being transmitted within the fiber from one end to the other. Fiberoptics is widely applied in medical practice to observe the human body internally. Fiberoptic fibers have also been used to transmit light signals carrying information from both electronic and optical sensors.
Limit switches presently in use require an external electrical power source and electrical wiring for operation. Many problems have been encountered in the past in providing electrical power to these limit switches. In particular, such electrical power adds to electromagnetic interference levels that can create problems with other equipment being used. Electrical wiring and signals are vulnerable to short circuits in saltwater areas. Additionally, in areas or in usages having high explosive potential (e.g., oil or gas wells and grain bins), there is an inherent danger of explosions caused by short circuits within the fires from the electrical circuitry.
The prior art discloses many types of fiberoptic switching systems. U.S. Pat. No. 3,886,544 is a keyboard using optical switching in which the incoming light from an optical fiber is transmitted to a different optical fiber upon the pressing of a button on a keyboard. U.S. Pat. No. 4,057,719 describes in electro-mechanically actuated light switch which transfers light energy into or out of a fiberoptic light transmission path. Liquid material contained within the switch provides a continuity between two fiberoptic terminals in the fiberoptic light transmission path. U.S. Pat. No. 4,116,531 shows a fiberoptic switch arrangement utilizing an unclad light guide arranged adjacent to a diaphragm of absorbing material. U.S. Pat. No. 4,170,731 teaches a fiberoptic control module and system for providing an on/off control to light passing within an optical fiber bundle. U.S. Pat. No. 4,283,114 teaches a fiberoptic light valve in which the light valve is utilized as a sensor to detect mechanical motion or displacement. A piezoelectric element responds to pressure to generate an electrical signal. U.S. Patent 4,303,303 describes a mechanical optical switching device utilizing triangular prisms to redirect incoming and outgoing light. Other switching devices for use in conjunction with fiberoptics include: U.S. Pat. No. 4,304,460; U.S. Pat. No. 4,318,587; U.S. Pat. No. 4,322,126; and U.S. Pat. No. 4,327,963.
None of the above-stated patents provides a system whereby a single optical fiber transmits light to and from the limit switch. Each of the above-stated patents teaches complicated, expensive, and cumbersome methods for switching light flow into and out of a fiberoptic arrangement. Furthermore, it is believed that the prior art has not incorporated beamsplitters, commonly found in laser technology, to shift the flow of light as needed to properly operate a limit switch-type design.
It is an object of the present invention to provide a limit switch having no electronic or electrical components adjacent the area in which the switch is utilized.
It is another object of the present invention to provide a fiberoptic switching system which utilizes a single optical fiber path for the transmission of the signal light.
It is another object of the present invention to provide a fiberoptic switching system incorporating beamsplitter technology for the transfer of light from one source to another.
It is a further object of the present invention to provide a fiberoptic switching technology which is of relatively low cost, simply installed, high efficiency and effectiveness, and of greater reliability.
It is still another object of the present invention to provide a fiberoptic switching system that provides an indicator pertaining to fiberoptic path integrity.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.